You can ignore Baitman's comment.
I've done a bit of digging around this thread and google, and currently this is the best data that we have.
The first is a late 2017
total copies update for RxL which gave us a total number of 460k, including print + digital. At first it was believed that this number gave us an estimate of 50% of the sales coming from digital sales. However,
razerxs pointed out that the number is misleading because it includes the
print number, not the physical sales number. This means that the number is inflated due to the large print number, lowering the supposed 50% digital metric.
Additionally,
this post from mrcho13 shows an estimated 230k copies sold (2 volumes), which also supports a smaller digital percentage. However, this number is shaky as it is a rough estimation from a third party using the numbers from shoseki (which I believe are already estimations themselves), so take this information with a grain of salt.
The second bit of information is
this early 2018 article. Here's the relevant information.
While this information might help the argument that digital sales make up 50% of the total sales,
it's important to note that this data takes into account the entirety of the manga volume market, meaning you can't just apply it to every manga that you happen to be biased towards.
Of course, Baitman up there likes to take this data and spin it into their own interpretation where 60% of Black Clover's volume sales are digital in order to push his agenda that it's a worldwide smash hit in the same vein of MHA. Funnily enough, they also made
this interesting comment. And I quote, "I dont think you could assume that every series is getting double its sales digitally just because one series RxL may perhaps be doing that". What an odd thing to say, coming from them.