With the Shadow of the Erdtree update to Elden Ring, all mods will be incompatible until they are able to update in a way that supports the latest version of the official game, or new mods are released specifically designed for SotE. If you wish to downpatch your game to version 1.10.1 to continue to use mods made prior to the update, use the following steps at your own discretion:

1) Go to %APPDATA%\EldenRing and make a backup of your ER0000.sl2 (vanilla) and ER0000.co2 (seamless) save files

2) Go to your Elden Ring Game directory and make a backup of your "EasyAntiCheat" folder

3) In Steam, right click Elden Ring... Properties... Updates... and set the game to "Only update this game when I launch it"

4) Navigate to your Steam Console using this link (if the link doesn't work for you just type "steam://open/console" into a browser or run prompt, or google how to access the Steam Console)

5) Use the following 2 commands:
download_depot 1245620 1245624 4173907165901381087
download_depot 1245620 1245621 4586391483365949586
and wait for the downloads to complete (this will take a while, as you're re-downloading Elden Ring)

6) Your downloaded files will be in Steam\steamapps\content\app_1245620\depot_1245624\ and Steam\steamapps\content\app_1245620\depot_1245621\
Move these files over to your Elden Ring folder, overwriting the existing files.

7) If you get a corrupted save error, run the game through Mod Engine 2 once with all mods disabled to port your base game saves over, then once again with only seamless co-op enabled to port your seamless co-op saves over to 1.10.1 (Unalloyed comes with an update_saves.bat script that will walk you through this)

To re-update, first restore your backed up Easy Anti-cheat folder (and save data if desired) and then right click Elden Ring in Steam and go to properties... Local Files... Verify Integrity of game files... 
and then launch the game from Steam to port your save data back and verify that the game works.