It's easy to find out. Navigate to Thunderbird Beta in F-Droid Basic and look at Versions. If you only have a single version there, then you have to delete it. If it says that no version with a compatible signature was found, so too. If you have three versions to choose from and one of them is installed, then you don't need to do anything, because then you will get updates.
You don't have to do anything. K-9 Mail remains K-9 Mail. A mistake was made in the naming process. This will be fixed soon. So in F-Droid the following will be present: K-9 Mail Thunderbird Thunderbird Beta
Thunderbird for Android is based on K-9 Mail, but has received a few changes here and there (e.g. the accent color is blue instead of pink). As mentioned above, K-9 Mail will remain and will probably continue to get the Beta & Stable versions in the version selector. Thunderbird has been split into two apps for this purpose. The settings should usually be able to be adopted from K-9 Mail and vise versa, because of the same codebase (but I haven't tested it). In the end, it's up to you whether you prefer the dog or the bird. :)
Edit: Added more info.
I have the tag function as in the picture in 132. Do you use any add-ons that have something to do with bookmarks? I couldn't find an option that affects this either. Not even in about:config.
I found 3 solutions, all of which have the same solution. You should enter a bookmark tag in the Bookmarks Manager so that this appears. It's probably a bug since Firefox 116. Solution 1, Solution 2, Solution 3.
Now it remains to be seen whether it will work for you.
Edit: Have linked solutions.
What device do you have? Do you have Android Vanilla / Android from the manufacturer, or do you have a Custom Rom? Sorry for the stupid question, but you only mentioned two keyboard apps. Have you tried other keyboard apps, for example Fossify Keyboard? Where did you get Lemmy from (Google Play, GitHub, F-Droid)?
First of all, the app is open source: https://github.com/mtotschnig/MyExpenses. In addition, the apps available in the official F-Droid repo are subject to regulations. And with the app there is no hint, with undesirable features. In addition, the app is also built again by the F-Droid team and if something is noticeable there, the building is interrupted.
I can recommend the app in my experience. I also purchased a license. It will connect to licencedb.myexpenses.mobi and validate the license. After that, you can block the app traffic with a DNS filter app (personalDNSfilter, RethinkDNS, etc.). At least that's what I did.
If you still have concerns, you can contact the developers at Mastodon (@myexpenses@mastodon.social).
You could use an RSS reader app and add a .rss to the end of a Mastodon URL. It works for individual accounts, hashtags, and instances.
Here is also a website where you can see if there is an open source port to non-open source games or an alternative that e.g. tries something of its own / based on the gameplay. As an example, the following "clones" are listed for Minecraft: Minetest, Mineclone2 (now VoxeLibre), ManicDigger and more.
Edit: fixed some grammatic fails.
To name a few: AssaultCube, Battle for Wesnoth, Cube2: Sauerbraten, FligthGear, Freeciv, Freeciv21, Nexuiz Classic, OpenArena, OpenHV, OpenRA, OpenTTD, Remnants of the Precursors, SpeeDreams, Stone Kingdom, SuperTux, SuperTuxKart, Unciv, Urban Terror, Veloren, Warozone 2100, Widelands, Xonotic
P.S. It may be that not all of them are FOSS, but they run natively on linux.
The Half-Life Games.
Looks right. Then you don't have to do anything. I mean, it's up to you, but do you really want to continue using the beta?