You are serving Menlo font on your website (monospace). This is not an open font. It is Apple IP and is not licensed for being served over the internet.
Although it is a derivative of the FOSS fonts-- Bitstream Vera and DejaVu, Menlo itself is not released with an open license. It's only meant for use with Apple devices.
I'd suggest changing to one of the many high quality FOSS fonts available online.
IMO the best workhorse sans font out there right now. OFL or otherwise. I've seen people dismiss every such font as a mere helvetica clone but they all miss out on the steady incremental improvements that each of such "clones" offer.
Inter is carefully crafted. It is uncommon to find OFL fonts that are hand tuned to such a degree (kerning and hinting). It is a beautiful and subtly unique take on a time tested design.
This site seems to use Apple's San Francisco Mono font in some places. Like for example in the ``Featured projects // 2020 Arctic Vault Program`` line. This font is only licensed to be used in/for Apple products. I'm on Ubuntu and do not have the font installed locally so they are clearly serving it remotely.
I wonder if it was some designer including it carelessly or if they legitimately found a way around the license.