I fear you may have misread my intention in comment; nothing nefarious intended, it’s about the “no updates to this app for years” which can equal “security issues unpatched” for the average, regular person. You did not disclaim the above details in your OP, you are NOT a normal user and had I known that I would never have commented.

Side comment, I find it more … interesting? (concerning?) they have “essential apps can’t run on 14” which to me is sort of a red flag event for those apps. $0.02 we’re up to 15 mainline with 16 coming soon, relying on apps stuck back on 13 never updated would not work for my conscious.

In addition to nifty.sh for UP as recommended, you might be interested in Conversations.im, an actively developed, well known XMPP client with mobile optimizations[1] to keep battery use low which can act as your UP broker (distributor) on the device. Note they talk about needing a proxy to convert message types at the bottom: https://unifiedpush.org/users/distributors/conversations/

[1] using two XEPs outlined on their site: https://conversations.im/#features -> Mobile optimizations