documentclass[a4paper,12pt]{article}

usepackage[margin=1 in]{geometry}
usepackage{ragged2e}
usepackage{booktabs, ltablex, makecell}
keepXColumns
newcolumntype{L}{>{raggedrightarraybackslash}X}
setcellgapes{5pt}
renewcommandtheadfont{smallbfseries}
renewcommandtheadgape{}
usepackage[strict]{changepage}
usepackage{pdflscape}

usepackage{lipsum}
begin{document}



    begin{landscape}
        tiny
        makegapedcells
        setlengthtabcolsep{5pt}
        begin{tabularx}{linewidth}{@{}>{bfseries}*{6}{L}@{}}
            caption{A wide table}\
            toprule
            thead{1}   & thead{2} & thead{3} & thead{4} & thead{5} & thead{6}\
            midrule
            lipsum[100]&lipsum[100]&lipsum[100]& lipsum[100]& lipsum[100]& lipsum[100]\
            lipsum[100]&lipsum[100]&lipsum[100]& lipsum[100]& lipsum[100]& lipsum[100]\
            lipsum[100]&lipsum[100]&lipsum[100]& lipsum[100]& lipsum[100]& lipsum[100]\
            lipsum[100]&lipsum[100]&lipsum[100]& lipsum[100]& lipsum[100]& lipsum[100]\
            bottomrule
%           endfirsthead

        end{tabularx}
    end{landscape}

end{document}