The most recent Crosswalk release was in 2016. The minimum version of Chrome we support on Android is Chrome 60, released in mid-2017. Chrome 60 is a great baseline to target and allows the following things without needing any build tools
- CSS Grid/Flexbox
- Arrow functions
- Template literals
And even then, that’s the bottom support from someone who hasn’t updated their phone in 5 years. Chrome 62 (late 2017) has dynamic imports. Chrome 67 (early 2018) has Big Int. Chrome 80 (early 2020) has nullish coalescing. Chrome updates independently of the phone’s OS, so there probably very few people actually on Chrome 60.
And the list goes on! Unless you’re using very cutting edge APIs that were drafted up within the last year or so, something like the Temporal API, you can get away with a lot without even needing to transpile your code.