Not sure how this got lost until now, but it should be straightforward to fix. https://noc.wikimedia.org/conf/highlight.php?file=timeline.php currently has:

} elseif ( $lang == 'zh' ) {
	$wgTimelineEpochTimestamp = '20161201000000';
	$wgTimelineFontFile = 'unifont-5.1.20080907';
}

We just need to make it || $lang == 'yue'

Change 667571 had a related patch set uploaded (by Aklapper; owner: Aklapper):
[operations/mediawiki-config@master] Fix broken rendering of characters in EasyTimeline for Yue Chinese

https://gerrit.wikimedia.org/r/667571

Any plans for the patch to be merged?

Change 667571 abandoned by Aklapper:

[operations/mediawiki-config@master] Fix broken rendering of characters in EasyTimeline for Yue Chinese

Reason:

Looks like I'm too stupid to rebase properly so I'll just abandon. Shrug.

https://gerrit.wikimedia.org/r/667571

Change 790016 had a related patch set uploaded (by Stang; author: Stang):

[operations/mediawiki-config@master] Set wmgTimelineDefaultFont to unifont for yue, wuu and zh_classical

https://gerrit.wikimedia.org/r/790016

Change 790016 merged by jenkins-bot:

[operations/mediawiki-config@master] Fix display issue of Timeline in cdo, gan, hak, wuu, yue and zh_classical

https://gerrit.wikimedia.org/r/790016

Mentioned in SAL (#wikimedia-operations) [2022-05-09T07:37:10Z] <kartik@deploy1002> Synchronized wmf-config/InitialiseSettings.php: Config: [[gerrit:790016|Fix display issue of Timeline in cdo, gan, hak, wuu, yue and zh_classical (T188997)]] (duration: 05m 13s)