FreeBSD

You can install FreeBSD under KVM and start learning. There is a qcow2 image on FreeBSD site so you can skip installation and boot right into the shell. And, start reading the handbook.

I have heard that there is some arrangement whereby you run FreeBSD on your hardware, with Linux in a bhyve virtual machine; you hand your physical wireless card into the VM, where LInux's drivers can talk with it; and route packets from the main system through it. -- Ah, https://blog.desdelinux.net/en/wifibox-the-project-that-allows-you-to-use-linux-wifi-drivers-in-freebsd/

To try to set up such a thing as your first entry into a BSD might be frustrating, but if you kept on until it worked, you would definitely have dived deep. (Dove? Doven? Diven?)

I'm a long-time Linux user now using FreeBSD on my home server. The first few times I looked at BSDs, they seemed old and stale, like nothing was happening there, and the coreutils were less comfortable to use because they were missing some switches. But what I've learned is that FreeBSD builds incrementally, without undermining itself, and my own understanding of it can do the same. What I've learned about previous versions of FreeBSD is more likely to still be true about the next version of FreeBSD.

BSD people often mention how the BSD in question is built as a whole, not cobbled together as a distribution. This difference can be stated far more quickly than it can be fully understood: like a culture, of which you gather a nuanced understanding from a broad survey of its literature, rather than a movement, whose goals are painted in broad strokes by a manifesto.

Anyway, welcome! My experience has been that #freebsd on libera.chat is more lively during US daytime hours than later at night. The Handbook is definitely your first documentation stop. ZFS, with its snapshots and replication, seems to be the most-hailed feature of FreeBSD; DTrace didn't even make the top 10, but when I didn't understand why NFSv4+Kerberos was failing, it was indispensable. Have fun!