Samsung Galaxy Tab S5e is no longer officially supported but you can install Android 11 OS on your android tablet, atleast unofficially. This will also increase the performance dramatically. Team behind Lineage is behind this endeavor.
How to install Android 11 on Samsung Galaxy Tab S5e tablet?
Unlock the bootloader. Connect to WiFi network and download the android 11 lineage ROM for Tab S5e from here.
Enable OEM Unlock in developer options
Turn off the tablet
Boot to download mode manually by plugging in USB and holding all the buttons for few seconds
Follow instructions on the screen
Connect to WiFi network and make sure OEM Unlock in developer options is still checked
Flash custom VBMeta image in Odin (use AP slot)
After flashing VBMeta, boot to stock. It’ll likely ask you to wipe data, if so do that
Connect to WiFi network and make sure OEM Unlock in developer options is still checked
Now you can flash TWRP in Odin, use AP slot once again, for convenience you can hold volume up while flashing it so that you boot to recovery right after it’s flashed
Install Lineage × whatever else you need (gapps, addon-su, …)
Format data and reboot (make sure to not install TWRP app when TWRP asks you to)