So I've noticed a couple things with BfA and this plugin (v0.3.2):

It tells me I ran King's Rest +3 this week when /raidinfo is all grey, and suggests I'm due for a 910 level weekly chest item (which is impossible).

Edit: I've got 0.3.2 installed which is supposed to include BfA fixes, but that seems off based on the details above.
Edit 2: The issue doesn't manifest until I change zones. When I initially login it registers properly that I haven't done a Mythic +.

Seems like this code block is wrong:

local chestRewardLevel = {
 [0] = nil,
 [2] = 910,
 [3] = 910,
 [4] = 915,
 [5] = 915,
 [6] = 920,
 [7] = 925,
 [8] = 925,
 [9] = 930,
 [10] = 935,
 [11] = 940,
 [12] = 945,
 [13] = 950,
 [14] = 955,
 [15] = 960,
};

There's a reference here that provides the BfA values: https://www.wowhead.com/news=285256/mythic-rewards-in-bfa-weekly-chest-can-contain-up-to-3-items-item-level-breakpoi#azerite-armor-weekly-chest-breakpoints

Do you accept pull requests? I'd be glad to submit a fix at least for the second issue.

I guess this has been abandon, closing.