Dhatura. I wanted to point out the main part of the question was how to Support the wall Before anything is put in for a lintel.
the easiest way would be to get a new steel lintel.
What do you mean by Steel Lintel? If this is an angle iron then how do you propose to get that back of the upright angel in the web areas? If your "lintel" is flat steel then its structurally bad.
A steel lintel in this application is also a bad marriage not to mention expensive.
1. First off that steel lintel needs to be gaged on its thickness to meet code, could require an engineered stamp for code acceptance. Pre formed Concrete lintels are to code on the get go at this length.
2. Second you have a less finished wall simply because you need to lay popcorn brick to fill in the inside ( I ) area for a finish look.
3rd since metal and mortar hasn't high adhesion qualities there needs to anchor bolts at the I beam ends to compensate for that steel to mortar marriage.
4th More so then not the bottom of the I beam needs an added welded flat steel plate to act as an Angle iron ledge to lay ( cement brick ledge) for a finished look.
So the all in all the "easiest way " is not cheap in this case.