I’m Russian and I’ve lived in Russia most of my life, I’m also into IT doing software testing so I think I can point you to the right direction. Below is the list of currently most popular Russian job boards to advertise your open positions:

HeadHunter https://hh.ru
This is the most popular job search platform in Russia with 47.97 mln monthly visits according to SimilarWeb stats. It is sort of LinkedIn but it doen't have the social feed. It is comparable to the CareerBuilder https://www.careerbuilder.com/ or Glassdoor https://www.glassdoor.com/in the US.

Habr Career https://career.habr.com/
Russian IT community blogs that runs their own job board. Similar to https://dev.to/, also popular among other post-Soviet countries. Many Russian IT companies maintain a blog there. 27.50 mln total monthly visits with 67% of them from Russian users according to SimilarWeb data.

Yandex.Rabota https://rabota.yandex.ru/
This is a job board by the Google of Russia. Similar to Google Jobs but it is dedicated job board where you can actually post the openings. Yandex is the largest search engine with 3 bln monthly visits according to SimilarWeb.

Github jobs https://jobs.github.com/
Although international, it is quite popular with Russian developers. SimilarWeb doesn't allow viewing the region stats but I've head about it in the Russian speaking IT community.

Djinni.co https://djinni.co/jobs/
A Ukranian job board with 1.5% of visit coming from Russian. Total monthly visits are 518.00K. Ukraine has got got really stong IT professionals. 1.5% of Russian users using this site are 99% remote-oriented so potentially they are your target audience too.

Telegram channels
Telegram is very popular in Russia with roughly 30 mln monthly user. I recommend checking out channel dedicated to posting jobs. The price is usually very affordable compared to the job boards and the conversion rates are comparable given that it is easy to share posts in Telegram. An example could be the channel that I maintain. It's called Remote Ever After https://t.me/remoteeverafter. You can DM me to and I'll be happy to share them with my audience.

Let me know if this is helpful and happy hunting!