Used to really enjoy these especially challenging with some added weight, I feel mobility or rather lack thereof makes it way more challenging too, more so than the actual (body) weight. Tight hip flexors I think are the main culprit, I noticed the first set usually being the hardest because of this. Maybe a bit of extra blood flowing to the muscles helps too.
See you're rocking those vivo's, I transitioned to barefoot shoes last summer around July. Really been enjoying my groundies and it even seems like my feet have grown over the last year, although I suspect it's the toes being less curled up because of all the extra space and movement they're getting. Hardly ever wear shoes in and around the house these days.
Recently been experimenting with the knee ability zero program from the kneesovertoesguy/athletic trurth group. Especially the atg split squat stood out for me as a great strength AND mobility builder. It builds from the ground up with plenty of regression options but more so starts at the ankle/lower leg rather than the foot. In my opinion it's a perfect next step after growing accustomed to minimalist shoes, might be interesting for you!
And keep up this great work, hive needs quality content like this :-)