Solved Joomla 4 migration KPATH_ADMIN error bricked site.

I was forced to update my Joomla version due to my host dropping PHP 7 before I was ready, and everything was going okay until I noticed I was getting an error from Kunena if I wasn't logged in as a user. It was the fairly unhelpful error message Undefined constant "Kunena\Forum\Libraries\Forum\KPATH_ADMIN". Trying several reported fixes did nothing, so I decided to temporarily put the forum into maintenance mode to prevent users from getting in, and that action seems to have spread the error message even into my admin backend now, completely bricking my site.

EDIT: I pulled off a miracle and got the backend back with some restoration of the tables. I'm still not 100% sure that I'm out of the woods, and I feel like this information might be helpful in some way so I'm leaving the post up. My question at this point is, what would cause this error to pop up for a guest but not a registered user?

Is there any hope for me or should I just find some other hosting software at this point?

This makes no sense, as support for PHP 7.x has expired and you will have to upgrade to PHP 8.x anyway. www.php.net/supported-versions.php

Joomla 3.10 with Kunena 5.2 would also have run with PHP 8.x.
Which versions (Joomla and Kunena) did you have installed before the upgrade?
Do you have a backup of your Jomla 3.x page? If so, copy it back and try the migration again. Follow these steps: docs.kunena.org/en/basics/upgrade/upgrade-k6-0

I had Joomla 3.12 I believe. I know I was 3.10 at least. Kunena was the latest version supported by Joomla 3. I redid the migration and the problem came back but only after I slept for the night. I opened a new browser window where I wasn't logged into the site and my home page gives me a 500 error. When I turn on better error tracing I get this nasty unknown KPATH_ADMIN stuff again.

I followed those update instructions to the letter. I didn't do anything wrong as far as I can tell.

I've attached the error page, and the config report below.

And just to clarify I was referring to ditching Joomla as I'm very sick of rebuilding my site from scratch every time they come out with a new major version that they insist will be an easy update but then never let any plugin makers catch up before circumstances force your hand into updating. Three of my other plugins don't work properly either so you're not the only forum I'm frequenting with the pressure of a busted site weighing me down.

Database collation check: The collation of your table fields are correct

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htaccess: Missing | PHP environment: Max execution time: 120 seconds | Max execution memory: 128M | Max file upload:

Kunena menu details:

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ID	Name	Menutype	Link	Path	In trash
1326	Forum	topmenu	Itemid=1316	kunena-2023-03-11	No
1316	Forum	kunenamenu	view=home&defaultmenu=1317	kunena	No
1317	Index	kunenamenu	view=category&layout=list	kunena/index	No
1318	Recent Topics	kunenamenu	view=topics&mode=replies	kunena/recent	No
1319	Unread	kunenamenu	view=topics&layout=unread	kunena/unread	No
1320	New Topic	kunenamenu	view=topic&layout=create	kunena/newtopic	No
1321	No Replies	kunenamenu	view=topics&mode=noreplies	kunena/noreplies	No
1322	My Topics	kunenamenu	view=topics&layout=user&mode=default	kunena/mylatest	No
1323	Profile	kunenamenu	view=user	kunena/profile	No
1324	Help	kunenamenu	view=misc	kunena/help	No
1325	Search	kunenamenu	view=search	kunena/search	No

Joomla default template details : cassiopeia_nab_network | author: Jared Petersen | version: 1.0 | creationdate: March 2023

Kunena default template details : Aurelia | author: Kunena Team | version: 6.0.9.1 | creationdate: 2023-02-22

Kunena template params:

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DefaultCategoryicon
profileIconset	default
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templatebyText
templatebyName
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Kunena version detailed: Kunena 6.0.9.1 | 2023-02-22 [ Git Repository ]
| Kunena detailed configuration:

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Kunena config settings:
boardOffline	0
enableRss	1
threadsPerPage	20
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messagesPerPageSearch	15
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| Kunena integration settings:

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Kunena - Finder Disabled
Kunena - AltaUserPoints Disabled
Kunena - Community Builder Enabled: access=1 login=1 activity=1 avatar=1 profile=1 private=0
Kunena - Easyblog Disabled
Kunena - Easyprofile Disabled
Kunena - Easysocial Disabled
Kunena - Gravatar Disabled
Kunena - JomSocial Disabled
Kunena - Joomla Enabled: access=1 login=0
Kunena - Kunena Enabled: avatar=1 profile=1

| Joomla! detailed language files installed:

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Joomla! languages installed:
cs-CZ	Czech (Čeština)
en-GB	English (United Kingdom)
en-US	English (United States)

Third-party components: None

Third-party SEF components: None

Plugins: None

Modules: Kunena Latest 6.0.2

Never had an .htaccess file? Rename the htaccess.txt file to .htaccess.
Disable the Kunena - Community Builder Integration plugin and the Kunena Latest module, then empty the cache and try to visit the frontend again.

Well I don't know about the htaccess file as we've always had one. Perhaps when the host restored the site it didn't copy over. Regardless I have a local backup for things like this.

Following your advice regarding the plugins and cache gets rid of the 500 error. I tested with reactivating them one at a time and Kunena latest doesn't seem to cause any issues but the CB integration brings back the same 500 error. Unfortunately my forums depend on this plugin so it isn't something I can just do away with.

According to the configuration report, you have not installed the Community Builder. In this case, the plugin must not be activated. If Community Builder is installed, the plugin should not cause an error.