=== Option Blow away your Config ===
TT, do you have a lot of config data that is important to you ? Its not in any way beyond impossibility that removing your config directory ( ~/.lazarus ) and starting again may clear your problem.
And your problem may relate to an issue Debian had in its early releases of Lazarus in Bullseye. Because they need to give it a special Debian version number, the first time Lazarus rebuilds itself, that was conflicting with the version it thought it was. Usually saw this as a threatening message at first startup after a rebuild.
Again, as discussed below, because after your very first rebuild, you are no longer using the Debian supplied binary anyway, removing ~/.lazarus may well solve your issue.
=== Option Update Lazarus (and maybe FPC) ===
TT, as I mentioned up near start of this thread, I recommend building from source rather than updating from either Debian Backports or even using the official Lazarus from SourceForge.
The reason is that if you are having problems (and a new install may well fix that but who knows ?) you are going to need to rebuild it with debug information anyway. But the Debian Backports and Official version from Source Forge both install your Lazarus up in read only space. Now, Lazarus is clever, when you rebuild normally (ie when adding a package) it makes out its rebuilding the original but in fact builds a new copy hidden down in your local config dir. Thats why the startlazarus command, it takes care of all that behind your back.
It works for normal, routine rebuilds but if you want to jump in there and add debug code and run it under gdb, it starts to get complicated.
You are going to rebuild Lazarus anyway, sooner or later, why not do it from the start and end up with a very straightforward install ?
Now, Bullseye has FPC 3.2.0, I don't remember if it will build Lazarus 2.2.4, anyone out there comment ? If so, leave FPC there but remove Lazarus with apt. Because of the complicated way Debian builds Lazarus, that will probably leave a lot of sub-parts of Lazarus behind, I like to use Synaptic to search for them and remove them manually.
If you need to replace FPC (because its too old to build Lazarus 2.2.4) then install a newer FPC, maybe from Backports or Testing if you feel brave.
=== Option Experiment in a Clone VM ===
Now, this is a VM we are talking about ? If its Virtual Box, you can make "linked clone" of your existing VM, experiment on that and blow the clone away, all making absolutely no change the the clone "Base". Now, I routinely use Testing like that and it always has a very current FPC/Lazarus installed. And pretty stable this late in their release cycle.
I bet taking a clone, removing your existing config, updating it all to Testing would solve your problem.
davo