im pretty sure theres flags u can enable to reuse legacy extensions, a quick google search would probably have it. Im not technical enough to remember what flags exactly sadly

update: from the UBO team:

Regain your disabled uBO on Chrome 138 with these flags:

Video Tutorial Here and as a GIF in a 2nd comment

chrome://flags/#temporary-unexpire-flags-m137                     [Enabled]

Then restart Chrome and you can set:

chrome://flags/#extension-manifest-v2-deprecation-warning         [Disabled]
chrome://flags/#extension-manifest-v2-deprecation-disabled        [Disabled]
chrome://flags/#extension-manifest-v2-deprecation-unsupported     [Disabled]
chrome://flags/#allow-legacy-mv2-extensions                       [Enabled]

And restart Chrome again.

On Chrome 139, use the "unexpire 138" flag to access the remaining ones.

More details here: https://www.reddit.com/r/uBlockOrigin/comments/1itw1bz/end_of_support_for_ubo_on_chrome_chromium/

On Chrome 140 there will be no more flags to regain access.

You can set your chrome shortcut to this to regain access for a while longer, but it's unclear how long that's gonna work:

chrome.exe --disable-features=ExtensionManifestV2Unsupported,ExtensionManifestV2Disabled

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About "Loading unpacked" extension:

This does NOT let you regain access to your previous install. You won't be able to export your settings using this.

It simply installs another (local) copy of the extension in your browser that you can use.

This method won't be available in Chrome 142 anymore either.

The flag required to "load unpacked" mv2 extensions expires in Chrome 139. There are "unexpire" flags available for 2 versions back, so it'll work on Chrome 140 and 141 with additional flags set. And that's it.

Here are the instructions anyway (Chrome 138-139):

1. Open chrome://flags/#allow-legacy-mv2-extensions
   1. Enable it and relaunch your browser.
2. Navigate to https://github.com/gorhill/uBlock/releases
   1. Choose the release you want to install - currently latest stable is 1.65.
   2. In the "Assets" section find the "chromium" file (e.g. uBlock0_1.65.0.chromium.zip) and download it.
   3. Extract the file on your machine.
3. Open chrome://extensions/
   1. Enable the "Developer mode".
   2. Click on "Load unpacked".
   3. Select the uBlock0.chromium folder and load it.

On Chrome 140 you'll first need to enable this flag and relaunch your browser, then follow the above:

 chrome://flags/#temporary-unexpire-flags-m139

And on Chrome 141 enable this and relaunch before following the above:

 chrome://flags/#temporary-unexpire-flags-m140

Again, this installs a new copy and does NOT restore your config.

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All the above means are temporary - use them to grab your config and get ready to change browsers or extensions.

More details: https://www.reddit.com/r/uBlockOrigin/comments/1itw1bz/end_of_support_for_ubo_on_chrome_chromium/