Google announced Linux app support in Chrome OS back at I/O, but the Pixelbook was the only compatible device at first. Chromebooks from Samsung and Acer have gained support since then, but Google's latest code addition to Chrome OS points to a raft of devices following suit very soon.
Chromium developers have just added support for Linux apps on all Apollo Lake-based Chromebooks. Intel's Apollo Lake processors include Celeron, Atom, and Pentium parts. According to XDA, there are at least 18 Chromebooks with these CPUs, most of which are focused on education. They include the Lenovo Thinkpad 11e, Acer Chromebook 11, Dell Chromebook 11, and more. They'll all have Linux app support when the updated Chrome OS rolls out.
As for when the updated code hits devices, that will vary on release channel. The additional Linux support will come first to Canary and Dev builds of Chrome OS in a few days. Chrome OS v69 should include the expanded Linux support when it hits the stable channel. Since these are mostly eduction machines, they're probably stuck on the stable release channel.