I migrated from ST to HA this year and haven't looked back, I got Home Assistant running and then took a big bang approach by unpairing everything from ST and then paired them to HA, I then wrote all my automations again, took a couple of days before everything was working again, I have 44 devices so didn't take too long. I also had 2 ZWave devices otherwise everything would've worked off a single dongle which was annoying.

Best of luck with the migration!

Although this is obviously a step in the right direction it needs to be followed up with security updates, no point increasing the life of the hardware without doing the same for the software.