Technically, the actual load and stress calculations are not as simple as you stated. The floor boards and adjoining structure will carry significant portions of the 2600 kg mass, therefore the angle brackets will not see all of the load.
If one assumes that the angle brackets do see all of the loading then:
2600 kg / 20 = 130 kg (287#) per angle bracket.
Area Moment of Inertia using the highest stress number (smallest 75 x 150 x 9 mm) from https://www.engineersedge.com/materi...gyration-7.htm
Iyy = 804812 mm^4
Cold Roller Steel E = 200 Gpa
Using beam deflection calculator at:
I get approximately 6.6 n/mm^2 at the support.. and a deflection so small the calculator does report it..
Your trailer can easily support a herd of well fed Americans...