Does Jexo have some demo environment to access and try the Foxly app?

You can create your own test environment by creating a free Jira instance Software.  Afterward creating the free Jira instance, you can install Foxly from the Atlassian Marketplace.

Both Jira Software and Foxly are free for up to 10 users, so you can invite 9 other colleagues to try Foxly for as long as you need.

For more info, Get started with Atlassian cloud for free, Foxly - Backlog Prioritization & Priority Planning Poker.