It looks like this is functionally a paid app.
Where are you seeing in-app purchases? I can’t find this anywhere in the app, and it’s not mentioned on F-Droid either (normally there is a disclaimer if there are non-free features).
You have to pay to get more icons on your home screen, which is pretty ridiculous.
I can’t find this anywhere in the settings. Every single toggle can be turned on and the number of home apps can be increased from 5 up to 30. Are you sure that you’re looking at the right app?
mLauncher has this feature. It is a fork of Olauncher, available on F-Droid and Google Play (and directly via GitHub). I have used it myself previously, it’s stable and customisable.
Take a look at this list. SHIFT from Germany is somewhat comparable to Fairphone in terms of modularity, HMD from FInland has also recently introduced some modular design into their phones. Note that these phonse are not manufactured in Europe, I’m not sure if any smartphone is. Another option not listed on that Wikipedia page is Mudita, from Poland, which is in the process of launching its first minimalist e-ink smartphone the Kompakt.

3 years of updates for flagships is not great.
Also, one of the upsides of Sony devices retaining critically endangered features like the headphone jack and microSD slot is that they appeal to geeks, which generally leads to to good custom ROM support. So it’s 3 years of updates from the manufacturer but you can often stretch their lifespan out a lot longer.

I agree that the future is bleak. I also agree that it makes life more difficult for those of us who don’t conform to this “I own nothing and pay a subscription for everything” lifestyle that people seem to be blindly moving in the direction of. I don’t pay for Spotify or any other streaming service (not that they even have all the music I listen to, I always hate it when people justify their existence with the “iT hAs EvErYtHiNG” line), I have my own music collection that I’ve curated over decades which is entirely offline. It won’t fit on a smartphone unless I pay a ridiculous amount of money for a model with tons of storage or convert my entire library to inferior quality. Ultimately it’s not a deal breaker feature for me so I do use a modern phone without external storage. I am fortunate that I own an MP3 player and multiple older phones with microSD support, including an XZ1 Compact which is what I currently use for portable music instead. It would be more convenient if I could just have everything on a single device like I used to, though.
It looks like someone is maintaining an unofficial LineageOS fork here. There doesn’t seem to be a lot out there, unfortunately. DivestOS being discontinued was quite a big blow to some of these older devices.

To quit in Firefox I have to tap to open a menu, then scroll down twice, then tap “quit”.
(Just replying in this thread since I can no longer access your other thread.)
I think the reason I overlooked this as an issue is because I have a phone with a 21:9 aspect ratio. The entire menu is always available, I never have to scroll to find things. I went back to a couple of my older phones with 18:5:9 and 16:9 aspect ratios and I can see what you’re talking about now. The shorter your screen is, the more this becomes an issue. Although on all of them it’s still only a single scroll so I’m not sure why you are being forced to scroll down twice.
Additionally, Google has already been targeted for its monopolising behaviour in the advertising space. It probably doesn’t want to add fuel to the fire by completely locking down its mobile ecosystem.