I never tested encryption on multirom. I don't keep it encrypted, I only have this device as a main device is hard to test all scenarios.
If you test something related to encryption let me know the result.
remember that TWRP can't backup or decrypt data encrypted on Oreo or Pie: no know workaround, one day TWRP will support it.
I was trying to encrypt secondary ROM but it seems it does not work. Some logo with an "android" is displayed for a while, then it UI is restarted but when the system gets back nothing happens. I've noticed also that system freezes after a while(even if I not trying to encrypt device) and phone becomes unresponsive(but the screen stays on). Could not run adb at the time so was not able to capture logs.
I thought that it's because I've made the secondary ROM from the backup of primary one so I've made a clean install of 7.0.2 as secondary.
At first boot it did not pass android logo(waited for some 5 minutes). Second time it reaches this "first time installation" screen, but then it said that System process becames unresponsive so I've to kill it. At third time it again displayed "first time installation" screen and after a while said that "intefrace" is not responding. I've gathered the logs(only logcat, adb shell was not working so could not get dmesg) from the last try
I've also installed your RR 5.8.5 as secondary(I thought that perhaps encryption will work there better) but it also freezes(so could not even get to the point of starting encryption). Unfortunately I haven't got logs from this try.
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Sorry, it looks like it just needed more time. Forth restart I've given it few more minutes and it stabilized and looks like is working just fine. Will try to gather logs from encryption
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I've tested again encryption. In the logs there is something like this:
07-26 10:58:04.367 308 3585 E Cryptfs : Unexpected value for crypto key location
07-26 10:58:04.367 308 3585 E Cryptfs : Cannot open block device