MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
create table t as
    select 'Table_A2_11_2021' as listtable union all
    select 'Table_L7_12_2021' as listtable union all
    select 'Table_C3_1_2021' as listtable union all
    select 'Table_D8_10_2021' as listtable union all
    select 'Table_T0_11_2021' as listtable union all
    select 'Table_E9_3_2021' as listtable union all
    select 'Table_L4_2_2021' as listtable union all
    select 'Table_O1_12_2021' as listtable union all
    select 'Table_P2_5_2021' as listtable union all
    select 'Table_Q2_10_2021' as listtable union all
    select 'Table_A3_12_2021' as listtable union all
    select 'Table_S5_9_2021 ' as listtable union all
    select 'Table_T8_11_2021' as listtable union all
    select 'Table_Q6_1_2021' as listtable
select min(listtable)
from t
group by substr(listtable, 7, 1);


min(listtable)


Table_A2_11_2021

Table_L4_2_2021

Table_C3_1_2021

Table_D8_10_2021

Table_T0_11_2021

Table_E9_3_2021

Table_O1_12_2021

Table_P2_5_2021

Table_Q2_10_2021

Table_S5_9_2021


select min(insert(listtable, 8, 1, ''))
from t
group by substr(listtable, 7, 1);


min(insert(listtable, 8, 1, ''))


Table_A_11_2021

Table_L_12_2021

Table_C_1_2021

Table_D_10_2021

Table_T_11_2021

Table_E_3_2021

Table_O_12_2021

Table_P_5_2021

Table_Q_1_2021

Table_S_9_2021