Um, actually, that’s an entirely different app. 
Meanwhile Mobian have been shipping a mobile friendly fork of GNOME To Do for a while.
Sadly I have no idea if upstreaming of Mobians patches is likely to happen anytime soon – given the age of the fork (Mobian ships this since some time in 2020), I guess it might not be a priority for upstream.
But there’s more:
Voicemail - There is no working voicemail app at the moment: Having the ability to easilly listen to voicemails is a must-have on a 2022 phone.
There’s an app for that - Visual Voicemail. It’s just a PureOS Store search for Visual Voicemail away 
Fractal - End-to-end encryption: At Yaal Coop we encrypt our conversations, so E2EE in Fractal is a blocker to us.
Fractal is going to deliver that, it works in fractal-next (when you can get that working ). Meanwhile, you can use https://hydrogen.element.io or https://cinny.in/ as Web Apps or install a different app. My recomendation would be Nheko, LinuxPhoneApps listing.
I could list a few hacks to mitigate other issues (e.g. using postmarketOS Tweaks to change the alarm sound of Clocks)… but time’s limited.
In general, if you’re looking for apps, I have this project, it is called LinuxPhoneApps.org, it’s far from perfect, but … it’s also not totally useless. Contributions welcome!