https://httparchive.org/reports/state-of-the-web#h2 on the HA website has a chart of the latest HTTP/2 stats. Is that what you’re looking for?
The query from March 2019 is still working for me and aligns with the stats on the website:
SELECT
_TABLE_SUFFIX AS client,
ROUND(SUM(IF(JSON_EXTRACT_SCALAR(payload, '$._protocol') = 'HTTP/2', 1, 0)) * 100 / COUNT(0), 2) AS percent
FROM
`httparchive.requests.2020_03_01_*`
GROUP BY
client
