Not sure if this is a Google issue but I only noticed it on my S10 after the Android 10 update. Apps in the Play Store take forever to install or update, they just hang at 99% or 100%. Doesn't matter if I'm on my home wifi, work wifi, cellular. Tried wiping cache partition, clearing Play store cache and data, disabling Google app, clearing Play store services cache and data. Nothing seems to get the apps to update or install quicker.
Facing the same issue here on the S10 5G, issue only occurs on wifi though which is strange because my wifi speed is 400mbps. Downloads from everywhere else are blazing fast but on the play store it sits at waiting for download for extended periods of time.
I'm pretty sure it's a bug with the play store itself. I have had the same issue with my Note 9 on Android 10 and 9. If doing what you are doing isn't working, then I'd recommend waiting. It will eventually install.
This issue seems to still happen occasionally, apps still will take forever to update or install. If I just leave my phone sit for several minutes it will eventualy go. Very annoying. This issue only started happening after the Android 10 update.