I found the following users who may fit your language exchange criteria:

Username	Date	Post Link	Relevance	Offered Matches	Sought Matches
u/brussels_london	2020-10-25	Post	`7`	English (C1)	Russian, Ukrainian
u/kingmickey9	2020-10-16	Post	`7`	English	Russian, Ukrainian
u/ekez_666	2020-10-24	Post	`7`	English (Native)	Russian, Ukrainian
u/thenaidenchop	2020-11-05	Post	`5`	English	Russian
u/jaybird2696	2020-11-21	Post	`5`	English	Russian

Please feel free to comment on the above posts to get in contact with their authors.