I have dreamt for years about fully migrating away from Google's services entirely. Whilst I have successfully moved personal emails onto a different service provider (I pay for web hosting, and can set up mailboxes as part of the service), calendars and address books were proving more difficult. However, the need was minimal, and so I contented myself with having rescued my email out of the 'G'-cosystem. I rarely used calendar appointments and invites in my personal life, and work was, well, work, and completely separate from my personal computing needs and preferences.
Recently however, I found myself needing to use non-G email for formal reasons (where a Gmail address just wasn't suitable), and with this need came the somewhat shocking realisation that I finally needed to use calendars for personal reasons. Having paid very little attention to this space for a few years, I was immediately surprised to discover quite a sophiscated Free Software product called Baïkal that touted both calendar and address book synchronisation (the official technology standards are "CalDAV" and "CardDAV", respectively).
My friends and readers will increasingly be aware that I place a great emphasis on Free Software (not open-source!) in my personal life for as many aspects of technology as possible. Whilst I am unable to become a 100% purist, I try to push towards that ideal bit by bit. I am content with evangelising the message as much as possible by using a Free Software operating system (currently Ubuntu Budgie 20.04; this latest 20.04 release was available for upgrade as of this morning).
As a side note, this new release plays much more nicely with my late 2019/early 2020 HP Spectre x360 13" (review coming soon); Ubuntu is usually excellent at reconciling idiosycratic hardware, but this laptop gave it a bit of a challenge in the previous release. The new kernel seems to have ironed many problems out, though.
Going back to the problem at hand, I quickly set up a new domain to install Baïkal, following the instructions on its website. The installation was painless; I was able to enable tasks (called "Todos" in Baïkal) and Notes too. I chose to use the default SQLite database instead of going through the trouble of creating yet another MySQL database for which I would forget the complicated password in minutes...
Baïkal just works. No faff, no fluff. The administration and setup are intuitive and easy.
For synchronising everything with Evolution on my laptop, I followed the excellent guide here. The same instructions worked perfectly on my Android phone after I installed OpenSync and Tasks from the Play Store. I can now get my calendars, address books, and todos/tasks synchronised between devices and can now actually send and receive useful meeting invites from people. I am still unsure how to get my Memos synchronised to the phone, but I can see that it works fine from Evolution on the laptop.
I have set up two other Baïkal servers now for other use cases and will be stress-testing it amongst friends soon. If it works, hopefully I can convince others to go on a bit of a G-diet too!