I think I had the same problem. Phone just kept rebooting after ubuntu installer flashed the recovery. I solved reflashing TWRP and then I cleared system, data and cache. After this procedure, the phone never rebooted again.
So i figured out in my case it would go black and then id force restart but it would ruin the install. So if u just unplug usb after the it says suggust it will do its thing. But if any oneis wondering i installed android 8 stock rom from xperifirm on windows10. Linux versiom coulnt get to work. Then i fastboot oem 7.1 binaries.
@4carlos Interesting, my Xperia x Compact, has the same battery life as my nexus 5. I do know lineageOS has really good battery management, which I could get that on UT 😛
but overall id say UT is the same battery life as a regular android or ios so its normal for me. LineageOS would really extend the battery to a couple days, not sure how they do it. They also have nothing really on that operating system
@unrealb2 I use Ubuntu Touch now.
The extreme slowness was caused by the wrong OEM binaries I used. It really was unusable then.
Now it isn't completely smooth either, but it is unproblematic and fine by me.