The new version is dog sh*t. Casting never worked on the beta experience. You have to side load an older version to keep casting. They seem to be having an issue with testing / QA. Just make sure you turn off auto update until they sort this mess out.
UPDATE
Further research found that the issue of not being able to find casting devices is adblockers blocking access to https://config.claspws.tv/. If you use piHole or similar check for that domain in your block logs. It worked for me on pfBlockerNG. Yay tracking!
Most likely the Google Play (arm64v8a) version is correct for modern devices.
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