The UK Department of International Trade are seeking expressions of interest from suitably qualified candidates who would like to be nominated to these rosters of arbitrators. Arbitration panels may be constituted from the rosters in accordance with the dispute settlement chapters of free trade agreements.
They're seeking to nominate people to serve on general dispute settlement rosters and specialised rosters for disputes related to financial services, sustainability or labour rights.
Deadline is just before midnight 6 December 2020.
See: https://www.gov.uk/government/publications/free-trade-agreement-fta-arbi...
It seems nationals of any country can apply.