from what i could find, there is a few ways to do it (using jailbreaking), but there are very few bootloaders for your device
https://forum.xda-developers.com/t/rooting-rct6773w22b-rca-voyager-ii.3394195/
https://www.infoworld.com/article/2622494/jailbreak--upgrading-a-non-upgradable-android.html
you may need do do some digging yourself so you can get more of a idea of how to jailbreak your RCA, but its the way to get more updates.