My first attempt was to flash the stock LineageOS and then install the microg packages from the fdroid store. I didn't manage to get that fully working, the microg self-check would have a lot of fails due to version mismatches. I never figured out why. A lot of applications complained about the lack of play services and warned me they wouldn't work, microg was clearly not installed properly.

Then, I flashed the "LineageOS for MicroG" ROM, which is a LineageOS fork with microg already installed. I had to enable all microg services but the self-check was 100% successful out of the box. No warnings about the lack of play services, everything was mostly working. I installed all software from Fdroid when possible and Aurora Store when not possible.

Push notifications were a bit of a struggle at first but they did work. I still didn't get notifications to work on Telegram, but "Telegram FOSS" fork seemed to work okay. For GPS/Maps I used Waze (which is technically owned by Google) and it worked flawlessly. I assume you can use other GPS application, I just didn't do my research on this one. For email I am using Proton Mail, which worked as expected.

The problematic apps were banking/financial apps, which I guess most people can live without. I'm confident the apps would work with microg but simply refused to even start. In Portugal our interbank network developed an application called "MBWAY", which is really ingrained in the portuguese population. Most people use it. It has a ton of cool functiontionality such as sending money to other people just by using the phone number (instantly and without fees), replacing your ATM/food cards for payments and generating virtual credit cards for online shopping.

I use MBWAY way too much (pun intended), and just decided I didn't want to live without it. I ended up flashing stock LineageOS and their GAPPS package, which contains the play services and play store app. I still install most stuff from the Aurora and Fdroid store. The banking/financial apps are now working.