You can filter by a tag (e.g., “exercise”) on your Beeminder dashboard like this: https://www.beeminder.com#exercise
There’s more details (e.g., two tags at once or negating a tag) at Advent 2022: 05. Tags for your Goals + Beebrowse & Altbee & BUI
The issue described in the thread you linked is that you can’t go from an unfiltered dashboard to a filtered one by just editing the URL and hitting enter. You have to either reload after hitting enter, or open the filtered view by entering the URL in a new tab. Similarly you can’t go from filtering by one tag to another tag without doing one of those workarounds. I believe this is because of the way browsers handle #... in URLs, rather than a Beeminder-specific problem.